4.7 Análisis del Comportamiento del consumidor
4.7.2 Matriz Importancia – resultado
4.7.1 Introduction
The purpose of this section is to describe common (platform) ABM operation with common terminology. For details about Power Share, refer to
paragraph 1.2.3.
4.7.2 Purpose
The purpose of ABM is to extend the life of valve regulated, absorbed electrolyte lead-acid (VRLA) batteries employed in standby service of an Uninterruptible Power Supply (UPS).
Studies on the “end of life” mechanisms of batteries in stand-by service reveal that the cause of battery failure is positive grid corrosion due to constant float charging. A key feature of ABM is that the batteries be held at rest rather than on float for most of their service life. This is accomplished by giving them a periodic freshening charge and allowing them to rest.
The length of time for the freshening and the timing of the initiating event can mitigate the benefit of rest. Care must be taken in limiting the initiating events for freshening so that the excess charging does not occur.
4.7.3 General Terms
battery rest – a battery state where it is neither charging nor discharging. This is done by disconnecting the battery from its charger.
charge mode - begins a charging cycle; the battery voltage is being recharged after discharging, after an extended inactive period, and when open cell voltage decreases below batOpChrgV in rest mode. The mode ends when the battery voltage reaches batChargeV, or if the mode has lasted batChargeTMax time.
charging cycle - consists of charge, float and rest modes. Battery voltage is charged in charge mode, then the voltage is kept steady in float mode, and finally batteries are inactive.
continuous-float charging - batteries are held at constant voltage,
batConstFloatV, instead of using a charging cycle scheme: user selectable.
float charging - during ABM cycling: charging at a higher voltage level than in continuous-float charging; used to bring all cells in a battery string to their full charge state. This is done for a limited duration.
float mode - after charge mode the battery voltage is kept constant at batEqualizeV during (batFloatTExt + batFloatT) time
OCV - open cell voltage
rest mode - batteries are inactive after float mode, without discharging nor charging.
VPC - volts per cell
4.7.3.1 Values and Limits
batChargeT - charge time: how long the charge mode lasted.
batChargeTMax – maximum charge time—default is 100 hours; the time-out for charge mode after which the float mode is started, even if the battery voltage has not yet reached batChargeV level.
batChargeV - charge voltage—default 2.335VPC / 25ºC; the level where charge mode changes to float mode.
batChrgI - charging current in charge mode.
batChrgRefV - charger voltage reference in charge mode—default 2.385VPC / 25ºC.
batConstFloatV - continuous-float voltage—default 2.30VPC / 25ºC: used to constantly charge batteries when ABM charging cycles are disabled by the user.
batDischT - cumulative discharge time—calculated internally by the UPS.
batEqualizeV - ABM cycling float mode voltage—default 2.30VPC / 25ºC.
batFloatT - ABM cycling float time—default 48 hours.
batFloatTExt - ABM cycling float time extension: batFloatTExt = 1.5 y batChargeT.
batMaxRestT - maximum rest mode time—default is 28 days: duration of rest mode, if neither discharging nor batOpChrgV have initiated a new charging cycle.
batMinDischT - minimum discharge time—default 20 seconds: limit for
cumulative discharge times after charge mode to initiate a new charging cycle.
batOpChrgV - opportunity charge voltage—default 2.10VPC; if battery voltage decreases below this limit in rest mode, a new charging cycle is initiated
immediately.
batRestFailT - battery OCV failure time—default 10 days in rest mode.
batSuppTestT - battery support test time moment—default 24 hours from the beginning of float mode.
batSuppTestV - low voltage limit for battery support test—default 1.75VPC.
4.7.3.2 Discharging
XCP Battery data block reports ABM status: discharging.
Discharging of batteries interrupts any charging mode. Cumulative discharging time is being calculated in batDischT.
If after a discharge period, the value of batDischT exceeds batMinDischT, then a new charging cycle is initiated; otherwise the previous charging mode is continued.
4.7.4 Charging Cycles
Battery Test 1
batSupTestT 24Hrs batEqualizeV 2.30V
Battery Test 2
30 seconds initial commissioning test;
50 seconds thereafter.
< 10days batRestFailT 8% of expected runtime (varies
based on batteries installed)
100Hrs max 48Hrs + 28 days
batFloatT + batFloatTExt
batChargeT batMaxRestT
batOCV 2.07V
Shoot for target when starting charge mode.
Stop at voltage to begin ABM float charge.
ABM is DISABLED - Constant Float charge level.
ABM Float charge level.
Starts charger if volt level is reached in <10days of rest mode.
For BTR, only used prior to a commissioning test.
For BTR, to determine the state of charge on battery.
If reached during battery test - cancels the test.
ACTIVE only after load loss when on battery, shuts logic power off & opens battery breaker.
DCUV level during battery mode, ”low battery shutdown alarm, logic power on only, starts 2 min. timer.
Absolute DCUV if reached prior to end of 2 min. timer.
BTR = Battery Time Remaining
Figure 26. Typical Battery Charging Cycle
4.7.4.1 Charge Mode
XCP Battery data block reports ABM status: charging.
When a battery is being charged, it is charged at the batChrgI constant current rate until it reaches a set voltage (batChargeV). The charging cycle is then changed to float mode.
While charging the battery voltage, the charger voltage reference is set to batChrgRefV, which prevents excessive battery voltage in the event of faulty battery voltage measurement.
The charge mode duration is measured and stored in UPS internal variable batChargeT. This data is used to determine the value of batFloatTExt.
4.7.4.2 Float Mode
XCP Battery data block reports ABM status: floating.
At initialization of float mode the value for batFloatTExt is calculated:
• batFloatTExt = 1.5 × batChargeT
The battery voltage is kept at constant voltage batEqualizeV for time (batFloatTExt + batFloatT).
Automatic Battery Support test (batSuppTestV) is done 24 hours after float mode begins.
4.7.4.3 Rest Mode
XCP Battery data block reports ABM status: resting.
The battery is effectively disconnected from the UPS. The rest mode lasts until:
• time defined by batMaxRestT has expired.
• the value of batDischT exceeds batMinDischT.
• the battery voltage has dropped below level batOpChrgV.
4.7.5 Temperature Compensation 4.7.5.1 Introduction
Battery temperature variation is compensated for by modifying battery-charging voltage.
In ABM charge and float modes, and when ABM charging cycles are disabled, the charger voltage reference is adjusted according to the highest battery temperature measurement. The adjusted values are:
• BattChargeV—the level where charge mode changes to float mode.
• BattEqualizeV—ABM cycling float mode voltage.
• BattConstFloatV—used ABM charging cycles are disabled by user setting.
BattChrgRefV is adjusted. This is the voltage reference value for the charger while in charge mode. If an ABM charging scheme is working properly this reference limit is never reached, but has changed to float mode at
BattChargeV.
The values are adjusted in temperature ranges from 0ºC to 50ºC. Outside of these limits, the values stay the same.
4.7.5.2 Algorithm
The compensation temperature range is from 0ºC to 50ºC, the voltage per cell is decreased 3 mV for each ºC. The EEPROM values mean the voltage levels at 25ºC. The charger values uses the following algorithm:
( )
T eeprom value mV(
T C)
value = _ −3 × −25°
T = battery temperature
Under 0ºC, value (0ºC) is used. Above 50ºC, value (50ºC) is used.
NOTICE
IEEE optimum temperature for battery life is 25ºC (77ºF).
Example
Using default values for the settings, the voltage values at some temperatures are:
Charging Voltage – Volts Per Cell
Parameter ºC 10ºC 25ºC 40ºC 50ºC
BattEqualizeV 2.380 2.350 2.305 2.260 2.230
BattChargeV 2.410 2.380 2.335 2.290 2.260
BattChrgRefV 2.460 2.430 2.385 2.340 2.310 BattConstFloatV 2.345 2.315 2.270 2.225 2.195
• BattChargeV = BattEqualizeV + 0.03 VPC
• BattChrgRefV = BattEqualizeV + 0.08 VPC
4.7.5.3 Disabled or Impossible Compensation
The temperature compensation can be disabled using a user setting. In this case, the EEPROM values (compensation values at 25ºC) are used directly.
Also, when the battery temperature measurement is not available, 25ºC is assumed.
4.7.6 Forcing on Rest Mode
There is an internal flag, ForceRestMode, which disables battery charging. For example, one of the building inputs in the unit can be directed to this flag.
When active, batteries are discharged when needed, but otherwise the flag forces the ABM rest mode. The original mode is resumed when the
ForceRestMode flag becomes inactive.
While forced on rest mode, battery failure testing/monitoring is not done.
While the ForceRestMode flag is active, discharging time (batDischT) is monitored normally. If it exceeds batMinDischT, then a new charging cycle is initiated when the ForceRestMode flag becomes inactive.
This flag also works when the ABM charging cycles are disabled by the user.
When active, the charging is disabled (rest mode is forced). When the flag becomes inactive, continuous-float charging is resumed.
4.7.7 User Disabling of ABM Charging Cycles
The user has the option of disabling the charging cycles and to select a continuous charging scheme. Cycling enabled is the factory default setting.
When batteries are not discharging, the charger functions to keep batteries at a constant voltage, defined by batConstFloatV.
Although batteries are charged constantly, the UPS keeps the normal ABM timer running. The operation is very similar to normal ABM cycling:
1. Charge mode begins when
- the cumulative discharging time (batDischT) exceeds batMinDischT
OR
- when time batFloatTExt + batFloatT + batMaxRestT has gone since the last charge mode.
2. Charge mode changes to float mode at batChargeV.
3. The external battery charger is controlled just as with normal ABM cycling: during charge mode and during float time extension, batFloatTExt.
4. Battery support tests are done normally, at a point defined by batSuppTestT, just as though cycling was enabled.
5. While in float mode, the battery voltage is kept at constant voltage, defined by batEqualizeV.
6. Rest mode is never entered, but float mode is continued over the batMaxRestT time at the batConstFloatV, except when ABM forced rest mode is initiated.
The differences to ABM cycling are:
• Float voltage is lower, batConstFloatV.
• There is no rest mode; float mode continues until cumulative discharging time (batDischT) exceeds batMinDischT, or batMaxRestT time has gone.
• Battery testing/monitoring is reduced: open cell voltage monitoring test is not done.
• The charge failure test measures charge mode time. This test is done normally, the only difference being a lower float mode voltage level.
• As the ABM cycling timing is internally running, the battery support test is done normally, just as when cycling was enabled.
• The ABM status is reported normally, charge or float. (including rest mode when in forced rest mode).
• The external battery charger is controlled just as with normal ABM cycling:
during charge mode and during float time extension, batFloatTExt.
4.7.8 Battery Failure Testing
Several battery tests are performed to try and determine the overall usability of the attached batteries, and to try and detect when the attached batteries will no longer provide adequate discharge time. Specific tests are performed to detect failed batteries and to detect battery end-of-life.
The tests that are covered in this section are:
• Battery test / Commissioning test (user initiated)
• Detection of failed (shorted) cell(s) caused by failure to reach float voltage
• Detection of failed (shorted) cell(s) caused by a rapid drop of open cell voltage in rest mode
• Detection of loss of capacity caused by failing to maintain cell voltage under load.
4.7.8.1 Battery test / Commissioning test
The battery test and battery commissioning test are almost identical, but the commissioning test is performed:
• the first time the unit batteries are initially charged for 24 hours,
• whenever the batteries are replaced,
• and whenever batteries are added or removed.
The results of this test are stored in EEPROM and are the baseline for
subsequent battery tests. The test consists of taking data when the UPS is at 2 levels, typically at 25% load and at 100% load. This topology is accomplished by running the rectifier and battery converter at the same time (Power Share mode). For more details on Power Share, refer to paragraph 1.2.3.
The Power Share control sets the rectifier sine reference magnitude to regulate battery power at the desired level. The rectifier is running in a constant current mode while the battery converter operates normally to regulate the rails.
Experiments have shown that running the second part of the test at or near full load yields the best results. If full load is not available at the output of the UPS, full load on the battery can still be achieved by allowing the rectifier to back-feed power to the utility.
Back-feeding the rectifier is the preferred method of running the test, but the user can disable back-feeding from the front panel.
If the user disables back-feeding, the second part of the test will be run with the available load, which must be at least 50% of the UPS rating. When the test starts, battery power is set to 25% of load. Unfortunately, when the load is first put on the battery, the voltage will drop, and then recover (termed “crack of the whip”). In order to get past this phenomenon, the test runs for 8% of the
expected runtime at load level 1 before taking the measurement. After test 1,
the power is set to test level 2 and run for 30 seconds on the initial
commissioning test, and for 50 seconds thereafter. The battery voltage and power level are recorded.
When the test executes, it will be transparent to the user. Unless the battery test detects a bad battery, there will be no beeping alarms and the front panel will not change state because the test is being performed. The XCP status will not change to “On Battery”. The battery test section of the LCD control menu will give an indication of test progress.
4.7.8.2 Battery Impedance / Open Cell Voltage Measurement
The battery impedance and open cell voltage will be determined by performing the following steps:Run test level 1 at 25% of the full UPS watt rating on the battery. The test duration is 8% of the expected runtime at this power level. The battery voltage and power are recorded at the end of test level 1. Current is also recorded for XCP battery data block only and does not impact runtime calculations.
Run test level 2 at the full available load for 50 seconds. After 50 seconds, battery voltage and power are recorded. Current is also recorded for XCP battery data block only and does not impact runtime calculations.
Calculate Open Cell Voltage:
( ) ( )
(Test Voltage Test Power Test Voltage Test Power) (Test Power Test Power)
Voltage Cell
Open = 1 × 2 − 2 × 1 ÷ 2 − 1
If this is a commissioning test, this voltage is stored as is; otherwise it is filtered with previous test results.
Calculate Battery Resistance:
(OpenCellVoltage Test Voltage) Test Power
impedance
Battery = − 1 ÷ 1
If this is a commissioning test, then calculated battery impedance is stored as both commissioning impedance and test impedance, otherwise:
( ) ⎟
= Batterytestimpedance calculatedbatteryimpedance filter impedance
If this is a commissioning test the battery health is set to 1, otherwise:
impedance
4.7.8.3 Cell Voltage Failure Under Load
When the unit drops on battery, the battery cell voltage is monitored during the first 25% of the discharge as determined by the battery runtime prediction. If the battery cell voltage drops below a certain level during the first 25% of discharge, “Battery Test Failed” is set. Failure of this test represents a loss of battery capacity and is not considered a potentially hazardous condition. This alarm is not stored in EEPROM and charging is not disabled as a result of test failure. This alarm is cleared when power is cycled, the batteries are replaced, or the battery test successfully completes. This test is active during the battery test/commissioning test.
The failure limit for this test is 1.833V/cell if expected runtime is greater than 15 minutes, or 1.81V/cell if expected runtime is less than or equal to 15 minutes.